746 Diseases of the Genital Organs 



perish is the basal embryo — that is, the embryo which is 

 located in the base of one horn nearest to the cervical canal 

 and whose embryonic sac extends across the uterine mouth 

 of the cervical canal into the opposite horn. The embryonic 

 sac of this basal fetus constitutes the "sentinel" which the 

 infection, more virulent than elsewhere, must pass in order 

 to imperil the lives of embryos beyond. This is strikingly 

 illustrated clinically in the dystocia of the sow dependent 

 upon fetal maceration and emphysema. The difficulty is 

 commonly with the basal fetus which, having perished and 

 undergone maceration at or near full term, since the occu- 

 pied segment of the uterus is paretic, can not be expelled, 

 and so bars the path of exit of the fetuses beyond, whether 

 living or dead. Consequently in a large proportion of cases, 

 if the basal fetus can be successfully removed, parturition 

 may proceed favorably. 



In multipara the death of one or more embryos has little 

 or no visible tendency to cause the uterus to contract and 

 empty its contents, so long as living and comparatively 

 healthy embryos remain, but the necrotic fetal cadaver or 

 cadavers, with the envelopes, remain in situ and undergo 

 maceration or desiccation. That is, the presence of an im- 

 mature, healthy embryo in the uterus serves to inhibit uter- 

 ine contractions which would expel indifferently dead and 

 living embryos. In this manner the reproductive efficiency 

 of swine is partly maintained although the average number 

 of young produced at a birth is greatly curtailed. 



The infections of the genitalia of swine have not been 

 comprehensively studied. Good and Smith, Hayes and 

 Traum, and others have searched for, and have frequently 

 found, the B. abortus in aborting sows, or have found that 

 the blood of aborting sows, or of boars to which aborting 

 sows were bred, reacted to the tests for that organism, and 

 concluded therefore that in these instances it was the es- 

 sential cause. Apparently other pathogenic bacteria were 

 not looked for and the conclusion that the B. abortus was the 

 causative agent was apparently based upon the assumption 

 thai tli»' B. abortus is tin specific cause of abortion in cattle, 



